How to make procedural very large/detailed volcano
A volcano can be approximated using an ANT landscape and a shader.





Procedure: (tested on Blender 2.79b)


Create the landscape using an ANT mesh and choose the 'vulcano' preset. Note you may need to enable the add-on for ANT in 'user preferences'






Switch to cycles render.
Create a new material for the landscape.
Add the following shader. This shader works by adding a red glow to the creases in the landscape using the pointiness property of the geometry. The height is used to control how far down the landscape the 'lava' flows.






Blend file with an example is available here